The present invention relates to head up display systems comprising a combiner and a projection unit such as used in aircraft, and more specifically to movement and stowage of the combiner of such a system.
A head up display (HUD) system is used in vehicles such as aeroplanes in order to overlay the user""s natural view (through, for example, a windscreen) with additional images in such a way that the natural view is not obstructed or obscured by the additional images.
Current HUD systems comprise a projection system mounted in the vehicle, generally above and out of sight of the user, projecting an image display from a projection unit onto a combiner, the direction of projection being substantially forward. The combiner, in use, is located in a deployed position which traverses the user""s line of sight in such a way that the projected image is reflected from the combiner to the user""s eyes. Light from an external field of view, meanwhile, passes through the combiner on the way to the user""s eyes.
In this way, it appears to the user that the external view is overlaid with the image which is projected from the HUD system.
When not in use, the combiner is usually moved from the deployed position to a stowed position, out of the user""s line of sight, in order to give the user as full an external field of view as possible. Current HUD systems, if they allow the combiner to be moved, enable movement of the combiner about a generally horizontal transverse axis towards and away from the projection unit. The presence of the projection unit prevents movement of the combiner completely outside the user""s field of view. Thus, some obstruction of the user""s normal field of view will still remain even with the combiner in the stowed position. Additionally, the stowed combiner will limit the freedom of movement of the user""s head, as well as presenting a possible hazard in the event of a crash.
It is among the objects of embodiments of the present invention to alleviate or obviate these and other disadvantages of the existing HUD system.
According to the present invention, there is provided a head up display system comprising a projection unit and a combiner wherein the projection unit projects an image onto the combiner, when the combiner is located in a deployed position, for reflection of the image towards the eye position of a user, the direction of image projection together with the direction of image reflection generally defining a projection plane;
the combiner being mounted rotatably on the projection unit such that the combiner may be reversibly moved between said deployed position and a stowed position in which said reflection does not occur;
the rotatable mounting taking the form of a pivot having an axis lying substantially in or parallel to the projection plane.
Preferably, the stowed position of the combiner is laterally offset from the body of the projection unit.
Preferably also the stowed position of the combiner is above the level of the lower surface of the projection unit.
Preferably the pivot is mounted on one side of the combiner and the projection unit.
Preferably the pivot comprises a sleeve surrounding a rod, the rod lying along the axis of rotation of the pivot.
Preferably also, one of said sleeve and rod is fixed in position, and the other of said sleeve and rod is rotatable and fixed to the combiner, such that rotation of said other of sleeve and rod causes rotation of said combiner about-the axis of rotation of said pivot.
Preferably the head up display system further comprises mechanical stops which define the stowed and deployed positions of the combiner.
Preferably the head up display system further comprises a motor and gear arrangement to control movement of the combiner between the deployed and stowed positions.
Preferably also the motor and gear arrangement comprises a gearwheel secured to the pivot, such that rotation of the gearwheel results in rotation of the pivot.
Preferably also the gearwheel is further linked to a motor by means of a series of intermediate gear wheels and axles, which transmit movement of the motor to the gearwheel secured to the pivot.
Preferably the motor is mounted on the exterior of the projection unit.